1. Field of Art
The present invention relates generally to pressure differential filtration, and in particular, to the structure of a rotary disc vacuum filter.
2. State of the Art
Rotary disc vacuum filters are well known in the art for separating suspended solids from a slurry. Typically, such filters have a tank to contain a slurry to be filtered; an elongated trunnion mounted to extend across the tank for rotation about a horizontal axis; and a plurality of disc-shaped filter elements comprised of wedge-shaped filter sectors, mounted at equally-spaced intervals along the trunnion to rotate with the trunnion into and out of the slurry in the tank. Further, such filters typically include a valve mounted to the tank in flow communication with the disc filter elements to selectively apply vacuum to the filter sectors of the disc filter elements.
Still further it is known to mount conduits on the exterior sidewall of the trunnion to provide flow communication between the valve and the filter sectors. Replaceability of these conduits is important in many applications because abrasive solids pass into the conduits with the filtrate and cause wear requiring replacement of the conduits within six months.
Various problems have been encountered when mounting conduits on the exterior sidewall of the trunnion in a manner facilitating replacement. For example, such problems include alignment of the filter elements with the conduits and alignment of the conduits with the trunnion and sealing the open end of the conduits from which the filtrate leaves the conduits. In one attempt to overcome the alignment problems, a plurality of fasteners are mounted along the conduits to fasten them to the trunnion. The plurality of fasteners are undesirable because of the time required to remove and reengage them. In another attempt to overcome both the alignment problems and sealing problems, a portion of the conduit is formed of flexible accordian-like material. The flexible portion is undesirable because the seals needed to connect the flexible portion to the conduit require time to remove and to replace and the material from which the flexible portion is made is itself susceptible to wear from the passage of abrasive solids.
Another problem encountered with conduits is with mounting the disc filter elements in flow communication with the conduits. It is known to weld a seat into openings along the conduits and to provide the sectors with a nipple at their bottom to insert into the seat to provide sealed flow communication between the sectors and the conduits. Welding seats into the openings of the conduits is undesireable; for example, the welding adds to the fabrication costs of the conduits and the seats are discarded with the conduits.